#define _CRT_SECURE_NO_WARNINGS 1

#include<stdio.h>

int main() // 1-n 相加
{
	int a = 1;
	int n = 0;
	int c = 1;
	int d = 0;
	scanf("%d", &n);

	for (a = 1; a <= n; a++)
	{
		c = c * a;
		d += c;
	}
	printf("%d\n", d);
	return 0;
}

int main() //1-n相乘
{
	int a = 1;
	int n = 0;
	int c = 1;
	scanf("%d", &n);
	for (a = 1; a <=n; a++)
	{
		c = c * a;
	}
	printf("%d\n", c);
	return 0;
}